Certain plating baths, in particular nickel and nickel-iron or other nickel alloy plating baths, will contain as additives organic materials. In many cases organics are complexers or reducers and as part of the reactions in the electrolytic baths, these organic compounds will decompose and/or react. A common decomposition or reaction product is the oxalate ion. The oxalate ion may be formed as a result of direct electrolytic decomposition or even of decomposition resulting from the presence of oxygen (or other oxidizers) formed at the anodes or introduced by air agitation. It is commonly formed in baths containing citric, malic, glutaric, gluconic, ascorbic, isoascorbic, muconic, glutamic, glycollic, aspartic, glucose, fructose, sucrose, dextrose, gluconate, ascorbate, erythorbate, other carbohydrates and the like.
As a result of the formation of the oxalate ion (however formed in the bath) a precipitate of insoluble nickel oxalate has been forming in these baths and, in particular, this precipitate (which may contain other occulded or absorbed materials such as carbonaceous materials or insoluble sulfides) has been forming in and about the anode bag cloth material. Eventually these anode bags become both hardened and clogged with this material so that flow of the electrolytic solution is impeded. When the process has proceeded far enough, it becomes necessary to remove the old bags and replace them with new ones, an expensive operation.
There are, in general, two ways that the insolubilizing cation can be introduced to the plating bath:
1. The cation could be added in the form of a soluble salt, e.g., as cerous chlorides. In such case beneficial actions may be obtained by general precipitation of the oxalate (i.e., cerium oxalate) in a form which does not clog the anode bags even though some is formed therein and by the fact that this other oxalate does not form the hardened matrix layer now formed by nickel oxalate. Of course, the precipitate must not deteriorate the electrodeposit. PA1 2. The cation could be introduced as part of a sparingly soluble salt and preferably before a filter element. In parallel to the case above, cerous fluoride may be added. In these cases locally higher concentrations of the sparingly soluble salt would cause exchange of the anions i.e. the sulfate or fluoride ion for the oxalate ion and so the general concentration of the oxalate in the body of the electrolyte would be kept low enough to prevent precipitation of nickel oxalate in the anode bags. PA1 (a) primary brightener; PA1 (b) secondary brightener; PA1 (c) secondary auxiliary brightener; and PA1 (d) anti-pitting agent. PA1 1,4-di-(.beta.-hydroxyethoxy)-2-butyne PA1 1,4-di-(.beta.-hydroxy-.gamma.-chloropropoxy)-2-butyne PA1 1,4-di-(.beta.-.gamma.-epoxypropoxy)-2-butyne PA1 1,4-di-(.beta.-hydroxy-.gamma.-butenoxy)-2-butyne PA1 1,4-di-(2'-hydroxy-4'-oxa-6'-heptenoxy)-2-butyne PA1 N-1,2-dichloropropenyl pyridinium chloride PA1 2,4,6-trimethyl N-propargyl pyridinium bromide PA1 N-allyl quinaldinium bromide PA1 2-butyne-1,4-diol PA1 propargyl alcohol PA1 2-methyl-3-butyn-2-ol PA1 thiodiproprionitrile ##STR1## thiourea phenosafranin PA1 fuchsin PA1 1. trisodium 1,3,6-naphthalene trisulfonate PA1 2. sodium benzene monosulfonate PA1 3. dibenzene sulfonimide PA1 4. sodium benzene monosulfinate PA1 5. saccharin PA1 1. To obtain semi-lustrous deposits or to produce substantial grain-refinement over the usual dull, matte, grainy, non-reflective deposits from additive free baths. PA1 2. To act as ductilizing agents when used in combination with other additives such as primary brighteners. PA1 3. To control internal stress of deposits, generally by making the stress desirably compressive. PA1 4. To introduce controlled sulfur contents into the electrodeposits to desirably affect chemical reactivity, potential differences in composite coating systems, etc. thereby decreasing corrosion, better protecting the basis metal from corrosion, etc. PA1 1. sodium-3-chloro-2-butene-1-sulfonate PA1 2. sodium .beta.-styrene sulfonate PA1 3. sodium propargyl sulfonate PA1 4. monoallyl sulfamide (H.sub.2 N--SO.sub.2 --NH--CH.sub.2 --CH.dbd.CH.sub.2) PA1 5. allyl sulfonamide PA1 6. diallyl sulfamide ##STR2## 7. sodium allyl sulfonate Such compounds, which may be used singly (usual) or in combination, have all of the functions given for the secondary brighteners and in addition may have one or more of the following functions: PA1 1. They may act to prevent or minimize pitting (probably acting as hydrogen acceptors). PA1 2. They may cooperate with one or more secondary brighteners and one or more primary brighteners to give much better rates of brightening and leveling than would be possible to attain with any one or any two compounds selected from all three of the classes: PA1 3. They may condition the cathode surface by catalytic poisoning, etc. so that the rates of consumption of cooperating additives (usually of the primary brightener type) may be substantially reduced, making for better economy of operation and control.